A measurement of the calorimeter response to single hadrons and determination of the jet energy scale uncertainty using LHC Run-1 $pp$-collision data with the ATLAS detector

TL;DR

This paper measures the calorimeter response to single hadrons in the ATLAS detector at the LHC, identifying a 5% modeling discrepancy and refining the jet energy scale uncertainty for high-momentum jets.

Contribution

It provides a detailed calibration of the calorimeter response to hadrons and improves the understanding of jet energy scale uncertainties using Run-1 LHC data.

Findings

5% discrepancy in calorimeter response modeling

Improved description of anti-proton response at low momenta

Jet energy scale uncertainty of 2-5% for jets above 2 TeV

Abstract

A measurement of the calorimeter response to isolated charged hadrons in the ATLAS detector at the LHC is presented. This measurement is performed with 3.2 nb$^{-1}$ of proton--proton collision data at $\sqrt{s}=7$ TeV from 2010 and 0.1 nb$^{-1}$ of data at $\sqrt{s}=8$ TeV from 2012. A number of aspects of the calorimeter response to isolated hadrons are explored. After accounting for energy deposited by neutral particles, there is a 5\% discrepancy in the modelling, using Geant4 physics lists, of the calorimeter response to isolated charged hadrons in the central calorimeter region. The description of the response to anti-protons at low momenta is found to be improved with respect to previous analyses. The electromagnetic and hadronic calorimeters are also examined separately, and the detector simulation is found to describe the response in the hadronic calorimeter well. The jet energy scale uncertainty and correlations in scale between jets of different momenta are derived based on these studies. The uncertainty is 2--5\% for jets with transverse momenta above 2 TeV, where this method provides the jet energy scale uncertainty for ATLAS.